SOHO Antenna Situation Improves

July 4, 2003

As often occurs in life, there is bad news and good news. High-rate transmissions (used to send its images and data) from the Solar and Heliospheric Observatory (SOHO) were initially interrupted on 27 June 2003. The interruption was expected due to a recent malfunction in the pointing mechanism of the spacecraft's high-gain antenna (HGA). For 2-3 week periods every 3 months, its high gain antenna will not be able to transmit any data back to Earth.

However, SOHO engineers found that medium-rate transmissions can be sent through its two omni-directional, low gain antennas when larger NASA Deep Space Network receiving stations are available. On the largest stations, with 70 meter dishes, even high-rate transmissions are possible. Medium-rate transmissions contain real-time science data, but does not have the capacity to dump on-board recordings of earlier gaps in contact.

Given this newfound capability, SOHO expects to experience only moderate data losses every day during the recurring 2-3 week periods. Full transmission is expected to return about July 14 until the next orbital problem period, expected to start on September 22. Scientists are quite relieved as SOHO is the only spacecraft that can effectively monitor certain solar storms, which can generate effects felt on Earth.

http://soho.nascom.nasa.gov/pickoftheweek/SOHOOrbit.jpg